While many conventional pedometers have been restricted regarding the position or direction in which the main unit is worn, there have been proposed in recent years body motion detecting devices wherein the wearing position and wearing direction can be freely set. Of these, there has been proposed a method and device for using multi-axial sensors to estimate orientation, while detecting body motion using the same sensors. This is advantageous in that lower costs can be realized as compared with a method wherein angular sensors or the like are used for estimating orientation.
For example, Japanese Unexamined Patent Application Publication No. 2004-141669 discloses a method wherein acceleration is detected by multiple body motion sensors having mutually different detection directions, an operating axis is determined/selected by analyzing signal patterns from the sensors, and ambulation is detected by signal analysis of the operating axis. Also, Japanese Unexamined Patent Application Publication No. 2005-140533 discloses a method wherein mutually-orthogonal bi-axial or tri-axial acceleration sensors are implemented, wherein the direction of motion of the body motion is estimated from a resultant vector from the sensor signals from each axis, and body motion is detected by analyzing the signal components on the direction of motion which has been estimated.